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Top-Down Network Design

Third Edition

Priscilla Oppenheimer

Priscilla Oppenheimer

Cisco Press

800 East 96th Street Indianapolis, IN 46240

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iii

Publisher: Paul Boger Manager, Global Certification: Erik Ullanderson Associate Publisher: Dave Dusthimer Business Operation Manager, Cisco Press: Anand Sundaram Executive Editor: Mary Beth Ray Technical Editors: Keith Nabozny, Joe Wilson Managing Editor: Sandra Schroeder Copy Editor: Bill McManus Senior Development Editor: Christopher Cleveland Book Designer: Louisa Adair Senior Project Editor: Tonya Simpson Proofreader: Apostrophe Editing Services Editorial Assistant: Vanessa Evans Composition: Mark Shirar Indexer: Tim Wright

About the Author Priscilla Oppenheimer has been developing data communications and networking sys- tems since 1980 when she earned her master’s degree in information science from the University of Michigan. After many years as a software developer, she became a technical instructor and training developer and has taught more than 3000 network engineers from most of the Fortune 500 companies. Her employment at such companies as Apple Computer, Network General, and Cisco gave her a chance to troubleshoot real-world net- work design problems and the opportunity to develop a practical methodology for enter- prise network design. Priscilla was one of the developers of the Cisco Internetwork Design course and the creator of the Designing Cisco Networks course. Priscilla teaches network design, configuration, and troubleshooting around the world and practices what she preaches in her network consulting business.

About the Technical Reviewers Keith Nabozny is a technology consultant with HP, an adjunct professor at Macomb Community College, and a graduate of Oakland University in Rochester, Michigan. He has three Cisco professional certifications and is a Certified Information Systems Security Professional (CISSP). Keith has supported large corporate clients for the past 14 years in operations, implementation, and engineering roles. He is currently supporting the firewalls of a major manufacturer with locations around the world. Most recently he taught network design and troubleshooting classes at Macomb Community College. Keith and his family live in Southeast Michigan. Joe Wilson , MSCS, PMC, CISSP No. 100304, is a senior network design engineer for TelcoCapital Systems, LLC. TelcoCapital is a leading provider of Cisco Unified Communications solutions for small and medium-sized enterprises. Joe is completing his dissertation toward a PhD in information technology at Capella University (Minneapolis, MN), with specializations in college teaching and IT security and assurance. Joe has worked in information technology for the past 20 years and is a retired systems engineer from The Boeing Company in Seattle, Washington, where he designed airborne NMS solutions for commercial aircraft. While working for AT&T Broadband Network Solutions as a broadband systems engineer, Joe designed commercial broadband net- works using advanced communications technologies such as ATM, SONET, DWDM, and Gigabit Ethernet. Joe has been a CISSP since 2006 and has distinguished himself as a trusted partner in providing secure communications solutions and services to public and private organizations. Joe teaches courses in the Cisco Networking Academy program at DeVry University in Federal Way, Washington.

iv Top-Down Network Design

Contents at a Glance

Contents

• Part I Identifying Your Customer’s Needs and Goals Introduction xxii
• Chapter 1 Analyzing Business Goals and Constraints
• Chapter 2 Analyzing Technical Goals and Tradeoffs
• Chapter 3 Characterizing the Existing Internetwork
• Chapter 4 Characterizing Network Traffic
• Part II Logical Network Design
• Chapter 5 Designing a Network Topology
• Chapter 6 Designing Models for Addressing and Numbering
• Chapter 7 Selecting Switching and Routing Protocols
• Chapter 8 Developing Network Security Strategies
• Chapter 9 Developing Network Management Strategies
• Part III Physical Network Design
• Chapter 10 Selecting Technologies and Devices for Campus Networks
• Chapter 11 Selecting Technologies and Devices for Enterprise Networks
  • Design Part IV Testing, Optimizing, and Documenting Your Network
• Chapter 12 Testing Your Network Design
• Chapter 13 Optimizing Your Network Design
• Chapter 14 Documenting Your Network Design - Glossary - Index
  • Part I Identifying Your Customer’s Needs and Goals Introduction xxii
  • Chapter 1 Analyzing Business Goals and Constraints
    • Using a Top-Down Network Design Methodology
      • Using a Structured Network Design Process
      • Systems Development Life Cycles
      • Plan Design Implement Operate Optimize (PDIOO) Network Life Cycle
    • Analyzing Business Goals
      • Working with Your Client
      • Changes in Enterprise Networks
      • Networks Must Make Business Sense
      • Networks Offer a Service
      • The Need to Support Mobile Users
      • The Importance of Network Security and Resiliency
      • Typical Network Design Business Goals
      • Identifying the Scope of a Network Design Project
      • Identifying a Customer’s Network Applications
    • Analyzing Business Constraints
      • Politics and Policies
      • Budgetary and Staffing Constraints
      • Project Scheduling
    • Business Goals Checklist
    • Summary
    • Review Questions
    • Design Scenario
• Chapter 2 Analyzing Technical Goals and Tradeoffs - Scalability - Planning for Expansion - Expanding Access to Data - Constraints on Scalability - Availability - Disaster Recovery - Specifying Availability Requirements - Five Nines Availability - The Cost of Downtime - Mean Time Between Failure and Mean Time to Repair
  • Network Performance
    • Network Performance Definitions
    • Optimum Network Utilization
    • Throughput
    • Throughput of Internetworking Devices
    • Application Layer Throughput
    • Accuracy
    • Efficiency
    • Delay and Delay Variation
    • Causes of Delay
    • Delay Variation
    • Response Time
  • Security
    • Identifying Network Assets
    • Analyzing Security Risks
    • Reconnaissance Attacks
    • Denial-of-Service Attacks
    • Developing Security Requirements
  • Manageability
  • Usability
  • Adaptability
  • Affordability
  • Making Network Design Tradeoffs
  • Technical Goals Checklist
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 3 Characterizing the Existing Internetwork
  • Characterizing the Network Infrastructure
    • Developing a Network Map
    • Characterizing Large Internetworks
    • Characterizing the Logical Architecture
    • Developing a Modular Block Diagram
    • Characterizing Network Addressing and Naming - Characterizing Wiring and Media - Checking Architectural and Environmental Constraints - Checking a Site for a Wireless Installation - Performing a Wireless Site Survey
    • Checking the Health of the Existing Internetwork - Developing a Baseline of Network Performance - Analyzing Network Availability - Analyzing Network Utilization - Measuring Bandwidth Utilization by Protocol - Analyzing Network Accuracy - Analyzing Errors on Switched Ethernet Networks - Analyzing Network Efficiency - Analyzing Delay and Response Time - Checking the Status of Major Routers, Switches, and Firewalls
    • Network Health Checklist
    • Summary
    • Review Questions
    • Hands-On Project
    • Design Scenario
• Chapter 4 Characterizing Network Traffic - Characterizing Traffic Flow - Identifying Major Traffic Sources and Stores - Documenting Traffic Flow on the Existing Network - Characterizing Types of Traffic Flow for New Network Applications - Terminal/Host Traffic Flow - Client/Server Traffic Flow - Peer-to-Peer Traffic Flow - Server/Server Traffic Flow - Distributed Computing Traffic Flow - Traffic Flow in Voice over IP Networks - Applications Documenting Traffic Flow for New and Existing Network
  • Characterizing Traffic Load - Calculating Theoretical Traffic Load - Documenting Application-Usage Patterns - Refining Estimates of Traffic Load Caused by Applications - Estimating Traffic Load Caused by Routing Protocols
    • Characterizing Traffic Behavior
      • Broadcast/Multicast Behavior
      • Network Efficiency
      • Frame Size
      • Windowing and Flow Control
      • Error-Recovery Mechanisms
  • Characterizing Quality of Service Requirements - ATM QoS Specifications - Constant Bit Rate Service Category - Real-time Variable Bit Rate Service Category - Non-real-time Variable Bit Rate Service Category - Unspecified Bit Rate Service Category - Available Bit Rate Service Category - Guaranteed Frame Rate Service Category - IETF Integrated Services Working Group QoS Specifications - Controlled-Load Service - Guaranteed Service - IETF Differentiated Services Working Group QoS Specifications - Grade of Service Requirements for Voice Applications - Documenting QoS Requirements
  • Network Traffic Checklist
  • Summary
  • Review Questions
  • Design Scenario
  • Summary for Part I
• Part II Logical Network Design
• Chapter 5 Designing a Network Topology
  • Hierarchical Network Design - Why Use a Hierarchical Network Design Model? - Flat Versus Hierarchical Topologies - Flat WAN Topologies - Flat LAN Topologies - Mesh Versus Hierarchical-Mesh Topologies - Classic Three-Layer Hierarchical Model - Core Layer - Distribution Layer
  • Access Layer
  • Guidelines for Hierarchical Network Design
• Redundant Network Design Topologies
  • Backup Paths
  • Load Sharing
• Modular Network Design
  • Cisco SAFE Security Reference Architecture
• Designing a Campus Network Design Topology
  • Spanning Tree Protocol
  • Spanning Tree Cost Values
  • Rapid Spanning Tree Protocol
  • RSTP Convergence and Reconvergence
  • Selecting the Root Bridge
  • Scaling the Spanning Tree Protocol
  • Virtual LANs
  • Fundamental VLAN Designs
  • Wireless LANs
  • Positioning an Access Point for Maximum Coverage
  • WLANs and VLANs
  • Redundant Wireless Access Points
  • Redundancy and Load Sharing in Wired LANs
  • Server Redundancy
  • Workstation-to-Router Redundancy
  • Hot Standby Router Protocol
  • Gateway Load Balancing Protocol
• Designing the Enterprise Edge Topology
  • Redundant WAN Segments
  • Circuit Diversity
  • Multihoming the Internet Connection
  • Virtual Private Networking
  • Site-to-Site VPNs
  • Remote-Access VPNs
  • Service Provider Edge
• Secure Network Design Topologies
  • Planning for Physical Security
  • Meeting Security Goals with Firewall Topologies
    • Summary
    • Review Questions
    • Design Scenario
• Chapter 6 Designing Models for Addressing and Numbering - Guidelines for Assigning Network Layer Addresses - Using a Structured Model for Network Layer Addressing - Administering Addresses by a Central Authority - Distributing Authority for Addressing - Using Dynamic Addressing for End Systems - IP Dynamic Addressing - IP Version 6 Dynamic Addressing - Zero Configuration Networking - Using Private Addresses in an IP Environment - Caveats with Private Addressing - Network Address Translation
  • Using a Hierarchical Model for Assigning Addresses - Why Use a Hierarchical Model for Addressing and Routing? - Hierarchical Routing - Classless Interdomain Routing - Classless Routing Versus Classful Routing - Route Summarization (Aggregation) - Route Summarization Example - Route Summarization Tips - Discontiguous Subnets - Mobile Hosts - Variable-Length Subnet Masking - Hierarchy in IP Version 6 Addresses - Link-Local Addresses - Global Unicast Addresses - IPv6 Addresses with Embedded IPv4 Addresses
  • Designing a Model for Naming - Distributing Authority for Naming - Guidelines for Assigning Names - Assigning Names in a NetBIOS Environment - Assigning Names in an IP Environment - The Domain Name System
    • Dynamic DNS Names
    • IPv6 Name Resolution
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 7 Selecting Switching and Routing Protocols
  • Making Decisions as Part of the Top-Down Network Design Process
  • Selecting Switching Protocols
    • Switching and the OSI Layers
    • Transparent Bridging
    • Selecting Spanning Tree Protocol Enhancements
    • PortFast
    • UplinkFast and BackboneFast
    • Unidirectional Link Detection
    • LoopGuard
    • Protocols for Transporting VLAN Information
    • IEEE 802.1Q
    • Dynamic Trunk Protocol
    • VLAN Trunking Protocol
  • Selecting Routing Protocols
    • Characterizing Routing Protocols
    • Distance-Vector Routing Protocols
    • Link-State Routing Protocols
    • Routing Protocol Metrics
    • Hierarchical Versus Nonhierarchical Routing Protocols
    • Interior Versus Exterior Routing Protocols
    • Classful Versus Classless Routing Protocols
    • Dynamic Versus Static and Default Routing
    • On-Demand Routing
    • Scalability Constraints for Routing Protocols
    • Routing Protocol Convergence
    • IP Routing
    • Routing Information Protocol
    • Enhanced Interior Gateway Routing Protocol
    • Open Shortest Path First
    • Intermediate System-to-Intermediate System
    • Border Gateway Protocol
    • Using Multiple Routing Protocols in an Internetwork
    • Routing Protocols and the Hierarchical Design Model
    • Redistribution Between Routing Protocols
    • Integrated Routing and Bridging
  • A Summary of Routing Protocols
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 8 Developing Network Security Strategies
  • Network Security Design
    • Identifying Network Assets
    • Analyzing Security Risks
    • Analyzing Security Requirements and Tradeoffs
    • Developing a Security Plan
    • Developing a Security Policy
    • Components of a Security Policy
    • Developing Security Procedures
    • Maintaining Security
  • Security Mechanisms
    • Physical Security
    • Authentication
    • Authorization
    • Accounting (Auditing)
    • Data Encryption
    • Public/Private Key Encryption
    • Packet Filters
    • Firewalls
    • Intrusion Detection and Prevention Systems
  • Modularizing Security Design
    • Securing Internet Connections
    • Securing Public Servers
    • Securing E-Commerce Servers
    • Securing Remote-Access and VPNs
    • Securing Remote-Access Technologies
    • Securing VPNs
    • Securing Network Services and Network Management
    • Securing Server Farms
    • Securing User Services
    • Securing Wireless Networks
    • Authentication in Wireless Networks
    • Data Privacy in Wireless Networks
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 9 Developing Network Management Strategies
  • Network Management Design
    • Proactive Network Management
    • Network Management Processes
    • Fault Management
    • Configuration Management
    • Accounting Management
    • Performance Management
    • Security Management
  • Network Management Architectures
    • In-Band Versus Out-of-Band Monitoring
    • Centralized Versus Distributed Monitoring
  • Selecting Network Management Tools and Protocols
    • Selecting Tools for Network Management
    • Simple Network Management Protocol
    • Management Information Bases (MIB)
    • Remote Monitoring (RMON)
    • Cisco Discovery Protocol
    • Cisco NetFlow Accounting
    • Estimating Network Traffic Caused by Network Management
  • Summary
  • Review Questions
  • Design Scenario
  • Summary for Part II
• Part III Physical Network Design
• Chapter 10 Selecting Technologies and Devices for Campus Networks
  • LAN Cabling Plant Design
    • Cabling Topologies
    • Building-Cabling Topologies
    • Campus-Cabling Topologies
    • Types of Cables
  • LAN Technologies
    • Ethernet Basics
    • Ethernet and IEEE 802.3
    • Ethernet Technology Choices
    • Half-Duplex and Full-Duplex Ethernet
    • 100-Mbps Ethernet
    • Gigabit Ethernet
    • 10-Gbps Ethernet
  • Selecting Internetworking Devices for a Campus Network Design
    • Criteria for Selecting Campus Internetworking Devices
    • Optimization Features on Campus Internetworking Devices
  • Example of a Campus Network Design
    • Background Information for the Campus Network Design Project
    • Business Goals
    • Technical Goals
    • Network Applications
    • User Communities
    • Data Stores (Servers)
    • Current Network at WVCC
    • Traffic Characteristics of Network Applications
    • Summary of Traffic Flows
    • Performance Characteristics of the Current Network
    • Network Redesign for WVCC
    • Optimized IP Addressing and Routing for the Campus Backbone
    • Wireless Network
    • Improved Performance and Security for the Edge of the Network
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 11 Selecting Technologies and Devices for Enterprise Networks
  • Remote-Access Technologies
    • PPP
    • Multilink PPP and Multichassis Multilink PPP
      • Authentication Protocol Password Authentication Protocol and Challenge Handshake
  • Cable Modem Remote Access
  • Challenges Associated with Cable Modem Systems
  • Digital Subscriber Line Remote Access
  • Other DSL Implementations
  • PPP and ADSL
  • Network Design Selecting Remote-Access Devices for an Enterprise
  • Selecting Devices for Remote Users
  • Selecting Devices for the Central Site
• WAN Technologies
  • Systems for Provisioning WAN Bandwidth
  • Leased Lines
  • Synchronous Optical Network
  • Frame Relay
  • Frame Relay Hub-and-Spoke Topologies and Subinterfaces
  • Frame Relay Congestion Control Mechanisms
  • Frame Relay Traffic Control
  • Frame Relay/ATM Interworking
  • ATM
  • Ethernet over ATM
  • Metro Ethernet
  • Selecting Routers for an Enterprise WAN Design
  • Selecting a WAN Service Provider
• Example of a WAN Design
  • Background Information for the WAN Design Project
  • Business and Technical Goals
  • Network Applications
  • User Communities
  • Data Stores (Servers)
  • Current Network
  • Traffic Characteristics of the Existing WAN
  • WAN Design for Klamath Paper Products
• Summary
• Review Questions
• Design Scenario
• Summary for Part III
• Part IV Testing, Optimizing, and Documenting Your Network Design
• Chapter 12 Testing Your Network Design
  • Using Industry Tests
  • Building and Testing a Prototype Network System
    • Determining the Scope of a Prototype System
    • Testing a Prototype on a Production Network
  • Writing and Implementing a Test Plan for Your Network Design
    • Developing Test Objectives and Acceptance Criteria
    • Determining the Types of Tests to Run
    • Documenting Network Equipment and Other Resources
    • Writing Test Scripts
    • Documenting the Project Timeline
    • Implementing the Test Plan
  • Tools for Testing a Network Design
    • Types of Tools
    • Examples of Network Testing Tools
    • CiscoWorks Internetwork Performance Monitor
    • WANDL Network Planning and Analysis Tools
    • OPNET Technologies
    • Ixia Tools
    • NetIQ Voice and Video Management Solution
    • NetPredict’s NetPredictor
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 13 Optimizing Your Network Design
  • Optimizing Bandwidth Usage with IP Multicast Technologies
    • IP Multicast Addressing
    • Internet Group Management Protocol
    • Multicast Routing Protocols
    • Distance Vector Multicast Routing Protocol
    • Protocol Independent Multicast
  • Reducing Serialization Delay
    • Link-Layer Fragmentation and Interleaving
    • Compressed Real-Time Transport Protocol
    • Requirements Optimizing Network Performance to Meet Quality of Service
    • IP Precedence and Type of Service
    • IP Differentiated Services Field
    • Resource Reservation Protocol
    • Common Open Policy Service Protocol
    • Classifying LAN Traffic
  • Cisco IOS Features for Optimizing Network Performance
    • Switching Techniques
    • Classic Methods for Layer 3 Packet Switching
    • NetFlow Switching
    • Cisco Express Forwarding
    • Queuing Services
    • First-In, First-Out Queuing
    • Priority Queuing
    • Custom Queuing
    • Weighted Fair Queuing
    • Class-Based Weighted Fair Queuing
    • Low-Latency Queuing
    • Random Early Detection
    • Weighted Random Early Detection
    • Traffic Shaping
    • Committed Access Rate
  • Summary
  • Review Questions
  • Design Scenario
• Chapter 14 Documenting Your Network Design
  • Responding to a Customer’s Request for Proposal
  • Contents of a Network Design Document
    • Executive Summary
    • Project Goal
    • Project Scope
    • Design Requirements
    • Business Goals
    • Technical Goals
    • User Communities and Data Stores